The invention relates to a mold for forming products. The invention relates in particular to such a mold for forming plastic products.
Mold-forming products provides the advantage that products can be manufactured relatively simply and reproducibly. Use can then be made, for instance, of injection molding technique. A disadvantage of this is that relatively high injection pressures are necessary to make the material spread throughout the mold cavity. Moreover, the injection temperature should be relatively high in order to prevent the material solidifying before the whole mold cavity has been filled. As a consequence, particularly high closing forces need to be applied to the mold, and stresses develop in the material and the product to be molded, which lead to an undesirably high degree of inaccuracy.
In existing molds, plastic is conventionally introduced into a part of a mold cavity with fixedly arranged wall parts. Accordingly, no solution to the above-stated problems is offered.
In existing compression molding techniques, plastic is introduced into the mold cavity with the mold partly open. Thus, the space in which the plastic is to be introduced is temporarily enlarged, so that less backpressure and moreover initially shorter flow paths are obtained. After the plastic has been introduced into the mold cavity, the mold is closed, so that the plastic is forced into the mold cavity so as to fill it completely. However, a partly open mold has considerable disadvantages, such as lack of precision, risk of plastic flowing away, unknown degree of filling of the mold cavity, and the like.
It has further been proposed to use a mold with at least one movable wall part of the mold cavity. In that way, with the mold closed, the resistance for plastic flowing in can be limited at least temporarily. Such molds are complex in construction because the injectors for the plastic are placed at a distance from and for instance opposite to such movable wall part. As a consequence, they need to be built into different parts of the mold, and for instance the or each injector will have to be able to move along with a movable part of the mold.